The doctoral candidate has one mentor or, in the context of a doctoral dissertation contract with a foreign university or institution, several mentors. A doctoral candidate may have a co-mentor, or exceptionally several co-mentors if this is necessary for his/her doctoral thesis. The doctoral candidate may also have an external adviser who contributes his/her specific knowledge to the doctoral thesis. An external advisor is an external expert from practice who contributes to the doctoral thesis (e.g. from business, public administration, cultural and artistic organisations, etc.).

Mentors and co-mentors in doctoral studies shall be university teachers with the title of assistant professor, associate professor or full professor, or academic worker with the title of scientific associate, senior scientific associate or academic counsellor, and shall demonstrate their research work, with the requisite bibliography, from the broader field covered by the doctoral dissertation. The minimum condition for proven research activity of a (co)supervisor, is a bibliography of the last five years that achieves 150 points according to SICRIS and has an index of important achievements A1/2 higher than 0 points or to have published at least two significant works in the last five years, as defined in the UL Habilitation Criteria and the faculties’ Annexes to these Criteria. For the purposes of determining eligibility as a mentor and a co-supervisor, significant scientific works for which the mentor or co-supervisor is the first or lead author shall be taken into account. In scientific fields where first or lead authorship does not exist or is not routinely demonstrated, the candidate's relevant contribution to these works must be clearly evident.

Mentors and co-mentors may also be persons with the appropriate habilitation of another institute (domestic or foreign) and who have references from the broader field covered by the topic of a doctoral dissertation, and who work in a study programme or are employed by an institute with whom the University of Ljubljana (UL) or a member faculty of the UL has concluded an agreement or entered into a cooperation agreement.

The mentor, the co-mentor and the external advisor shall be appointed by the Senate of the faculty which is conducting the procedure for the award of the degree of Doctor of Science or Doctor of Arts. The Senate of the faculty shall also decide on any change of the mentor, co-mentor or external advisor.

The conditions for the mentor, the co-mentor and the external advisor shall be verified by the competent authority of the faculty within three months of the doctoral candidate's enrolment in the doctoral programme. The mentor and/or external advisor may also be appointed by the Senate of the faculty at a later stage during the doctoral studies, on the proposal of the mentor and the doctoral candidate.

A mentor or co-mentor may serve in that role for a maximum of six doctoral candidates enrolled in any doctoral study programme at UL and no more than two years have passed since their last enrollment in the year or additional year. That number shall not include doctoral candidates who have submitted their dissertation for assessment